Migration velocity analysis and waveform inversion

Abstract

Waveform (output least squares) inversion of seismic reflection data can reconstruct remarkably detailed models of subsurface structure, and take into account essentially any physics of seismic wave propagation that can be modeled. However the waveform inversion objective has many spurious local minima, hence convergence of descent methods (mandatory because of problem size) to useful Earth models requires accurate initial estimates of long-scale velocity structure. Migration velocity analysis, on the other hand, is based on the Born approximation but is capable of correcting substantially erroneous initial velocities. Appropriate choice of objective (differential semblance) turns migration velocity analysis into an optimization problem, for which Newton-like methods exhibit little tendency to stagnate at nonglobal minima. The extended modeling concept links these two apparently unrelated approaches to estimation of Earth structure: from this point of view, migration velocity analysis is a solution method for the linearized (single scattering, Born) waveform inversion problem. Extended modeling also provides a basis for a nonlinear generalization of migration velocity analysis. Preliminary numerical evidence suggests that this new approach to nonlinear waveform inversion may combine the global convergence of velocity analysis with the physical fidelity of least squares.

Efficient full waveform inversion using the excitation representation of the source wavefield

“…Alternatively, Biondi & Almomin (2014) successfully inverts the full bandwidth of the data. Recently, the merger of migration velocity analysis with FWI (Symes 2008;Almomin & Biondi 2012;Allemand & Lambaré 2015;Wu & Alkhalifah 2015b;Alkhalifah & Wu 2016) has gained popularity in the context of improving the prospect of converging to a global minimum. Moreover, the isolation of desired wavenumbers in the gradient using conditioning and filtering (Albertin et al 2013;Tang et al 2013;Alkhalifah 2015;Kazei et al 2016) helps such convergence prospect.…”

Time-lapse image-domain tomography using adjoint-state theory

“…Adjoint-state methods (ASMs) have been used with success for many years in seismic exploration as an effective approach for calculating the gradient of a functional [see the overviews of Plessix (2006) and Symes (2009)]. Whilst the majority of studies focus on data-domain implementations -in particular, full waveform inversion (FWI) (Tarantola, 1984;Pratt, 1999) -a number of studies explore complementary image-domain tomography (IDT) strategies (Albertin et al, 2006;Yang and Sava, 2011).…”

Full waveform inversion using envelope-based global correlation norm

“…The common used approaches to extract long wavelength propagation velocities are traveltime tomography (Woodward et al, 2008) and migration velocity analysis (MVA; Symes, 2008). These two approaches have been widely applied to obtain initial models for FWI for real seismic data acquired for oil-exploration purposes (Ravaut et al, 2004;Operto et al, 2006;Malinowsky and Operto, 2008).…”

“…Using traveltime tomography, reliable picking of desired arrivals is an important component (Virieux and Operto, 2009) and MVA requires an extension in the image domain, which increases the computational cost (Symes, 2008), particularly in the 3D problem.…”